1. Field of the Invention
The present invention relates to an endoscope device, an endoscope and an image processing device for an endoscope, whereby normal white light images and fluorescence images can be observed.
2. Description of the Related Art
In recent years, endoscopes have come to be used widely in medical fields and industrial fields. Moreover, in medical fields, endoscope devices providing fluorescence images have also been achieved, in addition to endoscope devices providing standard images based on normal white light. As prior art examples of endoscope devices providing fluorescence images, the following devices have been disclosed, for example.
(a) U.S. Pat. No. 5,827,190
This U.S. Patent discloses a device for creating a fluorescence image and a non-fluorescence image. This device sequentially irradiates excitation light (400 to 450 nm) and illumination light (including 700 nm) endoscopically and receives fluorescence and reflected light generated by human tissue by means of image pickup elements, whereby the respective signals are displayed on a monitor in such a manner that an affected tissue and a normal tissue can be distinguished.
Moreover, this patent also discloses lengthening the irradiation time of the excitation light beyond that of the non-excitation light (illumination light), and improving the brightness (S/N) by incorporating a CCD in the distal end of the endoscope and synthesizing the CCD pixels when capturing an image of the fluorescence (when irradiating excitation light).
(b) Japanese Patent Laid-open Publication No. H10-151104
This patent discloses a device which sequentially displays a normal-light image and a fluorescence (infrared) image. This device comprises a rotational filter for a normal-light image and a rotational filter for a fluorescence image, provided in concentric fashion, in such a manner that the rotational filters are moved according to the modes (FIG. 12 to FIG. 17 of the patent). Moreover, this device comprises an optical aperture through which infrared light is transmitted, provided at the distal end of the endoscope, whereby brightness is improved in fluorescence mode, since a large amount of infrared light is transmitted. The opening for visible light is restricted by the optical aperture (see FIG. 6 of corresponding patent), and hence the resolution is increased.
(c) Japanese Patent Laid-Open Publication No. H10-201707
This patent discloses a device for sequentially displaying a normal-light image and a fluorescence image, wherein by switching the modes (normal-light image and fluorescence image) with respect to red+infrared, G and B rotational filters disposed at a light source, either a filter transmitting visible light or a filter transmitting infrared light are selected (FIG. 9 to FIG. 11 of corresponding patent).
(d) Japanese Patent Laid-Open Publication No. H8-140928
This patent discloses a device for simultaneously displaying a normal-light image and a fluorescence image. This device comprises an image pickup element for capturing a normal-light image and an image pickup element for a capturing fluorescence image, disposed at the distal end of the endoscope. Moreover, it is disclosed that RGB light is sequentially irradiated from a light source, fluorescence being imaged when B light is irradiated.
(e) Japanese Patent Laid-Open Publication No. H8-140929
This patent discloses a device for switching between and displaying a normal-light image and a fluorescence image. An image pickup element for capturing a normal-light image and an image pickup element for capturing a fluorescence image are disposed at the distal end of an endoscope. In this device, in fluorescence mode, the fluorescence image is taken as a B signal, and only the B signal is displayed on the monitor.
(f) Japanese Patent Laid-Open Publication No. H9-66023
This patent discloses a device which synthesizes and simultaneously displays a normal-light image and a fluorescence image. In this device, an image pickup element for capturing the normal-light image and an image pickup element for capturing the fluorescence image are disposed in the distal end of the endoscope. In this device, R, G, B light and excitation light (or white light and excitation light) are irradiated sequentially from a light source, and the fluorescence image is captured when excitation light is irradiated.
(g) Japanese Patent Laid-Open Publication No. H9-70384
This patent discloses a device which synthesizes and simultaneously displays a normal-light image and a fluorescence image. This device comprises an image pickup element for capturing the normal-light image and an ultra-sensitive image pickup element for capturing the fluorescence image, disposed at the distal end of the endoscope. In this device, R, G, B light is irradiated sequentially from a light source, and the fluorescence image is captured when blue light is irradiated.
(h) Japanese Patent Laid-Open Publication No. H10-225427
This patent discloses an electronic endoscope device which is capable of capturing a fluorescence image. In this device, if a fluorescence image is dark, then an optical aperture of the light source is opened and some pixels of image pickup are combined to enlarge the pixel size.
In the endoscopes described in Japanese Patent Laid-open Publication Nos. H8-140928, H8-140929, H9-66023, H9-70384, mentioned above, in order to observe both a fluorescence image and a normal-light image, both an image pickup element for capturing a normal-light image and an image pickup element for capturing a fluorescence image are disposed at the distal end of the endoscope. Therefore, such conventional endoscopes have drawbacks that the insertable parts are too thick, the endoscopes are expensive due to the necessity of providing two image pickup elements, and the like.
In the endoscopes described in Japanese Patent Laid-open Publication Nos. H8-140928, H8-140929, H9-66023, H9-70384, mentioned above, in order to observe both a fluorescence image and a normal-light image, both an image pickup element for a capturing normal-light image and an image pickup element for capturing a fluorescence image are disposed at the distal end of the endoscope, and excitation light of only one particular wavelength can be irradiated. Therefore, in order to change the wavelength, it is necessary to replace the rotational filter, and if endoscopic examination is to be performed whilst changing the wavelength, then the laborious task of replacing the rotational filter is required, and time is also required for the endoscopic examination.